Flapper check valves are known in the art which are flat in configuration and have multiple leafs integrally stamped from flat spring steel stock which are adapted to cover and seal multiple ports in a flat plate or housing surface, such leafs being adapted to flex to an open position when the pressure differential is higher on the sealed port side of the flapper valve. The assembly of such valves normally involves discreet housing and backup provisions, if any, which do not readily accommodate simple insertion in a plate, an airline tube or cylindrical passage to operate as a one-way check valve.